The present invention relates to a rear dumping dragline bucket and rigging system (rear dumping dragline bucket) that has a tailgate that will be released/opened when the bucket is tilted rearwardly enough so that the rigging is oriented in a selected manner, and which will be automatically reset when the bucket returns to its operative position.
Various rear dumping dragline buckets have been advanced in the prior art. An early excavating bucket which had a latched door at the rear end is illustrated in U.S. Pat. No. 955,285. This patent, however, had a single latch in the center of the door, and utilized a separate arrangement whereby the bail on the bucket, which was pivotally mounted and attached to the hoist line, would pivot forwardly and have a latch dog member that engaged a bellcrank, which in turn operated on a link that hooked another bellcrank which was used to lift the latch to undo the rear door. It is apparent that the total pivoting of the bail required a substantial amount of movement of the bucket, into a vertical position, before unlatching, and the use of mechanically engageable members would be likely to be unreliable.
U.S. Pat. No. 1,118,724 also shows a shovel bucket that has a rear dump door controlled by a rather complex latch that is operated through a lever and chain arrangement. The chain is driven by a separate sheave that would be rotated to pull the chain and release the latch.
Various other buckets that have rear dumping capabilities with doors that are latched during loading and swing, and unlatched by various apparatus have been advanced in the art, but a fully reliable arrangement that provides for essentially automatic operation on a fool-proof basis has been lacking. A bucket which permits rear dumping, but without a separate door is shown in U.S. Pat. No. 5,400,530.
A rear dumping dragline bucket will increase the efficiency of operation of a dragline by permitting discharging overburden at a greater dump radius distance from the dragline power unit and depending on individual hoist rigging requirements, at a higher height than with a forward dumping bucket and rigging system. A need thus exists for a reliable rear dumping bucket.